1. Field of the Invention
The present invention relates to an imaging apparatus and an audio processing apparatus.
2. Description of the Related Art
There is a digital camera on market which includes a function for capturing moving images and recording audio signals, in addition to capturing still images. When capturing a moving image, a capturing state of the digital camera changes, so that a drive unit of the digital camera operates to drive a focus lens, or to drive a diaphragm mechanism in response to a change in brightness. The operation of the drive unit thus generates noise in the audio signal being recorded. To solve such a problem, there is a technique for reducing such drive noise.
Japanese Patent Application Laid-Open No. 2006-279185 discusses an imaging apparatus that performs a spectral subtraction method which is one method of cancelling noise. When a user operates on a zoom key for driving a zoom lens of the imaging apparatus employing such a method, the image apparatus performs noise cancellation on the audio signal input through a microphone in synchronization with driving of a zoom lens drive motor.
Further, Japanese Patent Application Laid-Open No. 2006-287387 discusses a technique for executing noise cancellation as described below. A reference microphone is placed near a drive motor that generates the drive noise. When the drive noise input to the reference microphone exceeds a predetermined level, noise cancellation is performed. Since the noise is detected based on the signal input to the reference microphone, a time lag between timing at which a drive signal is transmitted to the drive motor, and timing at which the drive noise is generated by actually driving the drive motor, is reduced.
Furthermore, Japanese Patent Application Laid-Open No. 2001-344000 discusses a technique for accurately detecting sudden noise that is generated in a communication apparatus such as a cellular phone which encodes and transmits the audio signal. More specifically, the audio signal acquired in performing communication is divided into frames of a predetermined time length, and the signal for each frame is then transformed to frequency domains. The change in the signal level is then monitored for each frequency domain, so that the sudden noise is detected.
However, it is necessary for the noise cancellation technique that cancels the noise in the audio signal to accurately determine a section in which noise cancellation is to be performed. The technique discussed in Japanese Patent Application Laid-Open No. 2006-279185 determines the section in which noise processing is to be performed according to timing of the zoom key operation. If the timing signal is imprecise, noise processing cannot be accurately performed.
Further, it is necessary in the technique discussed in Japanese Patent Application Laid-Open No. 2006-287387 to use a separate reference microphone for acquiring the noise, in addition to the main microphone for inputting the audio signal. Number of parts thus increases when employing such a technique. Furthermore, since it is necessary to continuously supply power to the reference microphone, power consumption increases in the digital camera.
Moreover, it is necessary in the technique discussed in Japanese Patent Application Laid-Open No. 2001-344000 to constantly transform the signals for each frame to the frequency domains while inputting the audio signals. Further, Fourier transformation which is commonly used in performing frequency domain transformation becomes a heavy load in terms of an amount of calculation.